Responses to an April 2018 government survey have now been collated, creating a list of 15000 Spanish taxpayers that hold cryptocurrency.
source https://www.google.com/url?rct=j&sa=t&url=https://news.coinsquare.com/government/spanish-treasury-tracking-cryptocurrency-owners-to-ensure-tax-payments/&ct=ga&cd=CAIyGmM2Nzk3ODA2ZWViNjVjODI6Y29tOmVuOlVT&usg=AFQjCNHevtVp34OuMpM5Sr5U2AlQKwV-Kg
